The available storage media capacity for personal video recording increases continuously, approximately doubling every 2 years. Currently it is possible to store about 20 full-length movies on a single 100 GByte hard disk. In 2005, it will likely be possible to store about 80 movies on a single 400 GByte hard disk.
Similar figures apply to optical recording: currently about 5 GByte can be stored on a single layer single sided DVD disc but the DVR recorder as a successor of the today's DVD recorder will allow storage of up to 35 GBytes on a corresponding disc. Furthermore, two or even more layers can be used per side and these can be applied to both sides of the disc. Finally, it is possible to combine several discs in a special magazine.
This enormous amount of data requires new ways to organize the recordings, search for content and access specific recordings, because it is no longer possible to find recordings in a user's book shelf by just looking at the video cassettes/discs and some annotations on their cover. One possible solution for this is to use so-called metadata, defined as data about data, for the recorded content.
Metadata can be embedded within the multimedia content itself. For example, the MPEG-2 systems standard as specified in ISO/IEC 13818-1 defines program specific information (PSI) which is multiplexed with the audio and video streams. Similarly, the DVB standard used for the transmission of digital television signals specifies Service Information (DVB-SI) included in a DVB compliant MPEG-2 transport stream multiplex.